Mayo Clinic Health Library

Prediabetes

Updated: 01-26-2012

Definition

Prediabetes means that your blood sugar level is higher than normal, but it's not yet high enough to be classified as type 2 diabetes. Still, without intervention, prediabetes is likely to become type 2 diabetes in 10 years or less. And, if you have prediabetes, the long-term damage of diabetes — especially to your heart and circulatory system — may already be starting.

There's good news, however. Prediabetes can be an opportunity for you to improve your health, because progression from prediabetes to type 2 diabetes isn't inevitable. With healthy lifestyle changes — such as eating healthy foods, including physical activity in your daily routine and maintaining a healthy weight — you may be able to bring your blood sugar level back to normal.

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Symptoms

Often, prediabetes has no signs or symptoms.

Darkened areas of skin, a condition called acanthosis nigricans, is one of the few signs suggesting you are at risk for diabetes. Common areas that may be affected include the neck, armpits, elbows, knees and knuckles.

Classic red flags of type 2 diabetes to watch for include:

  • Increased thirst
  • Frequent urination
  • Fatigue
  • Blurred vision

When to see a doctor
Consult your doctor if you're concerned about diabetes or if you notice any type 2 diabetes signs or symptoms — increased thirst and frequent urination, fatigue, and blurred vision.

Ask your doctor about blood glucose screening if you have any risk factors for prediabetes, such as:

  • You're overweight, with a body mass index above 25.
  • You're inactive.
  • You're age 45 or older.
  • You have a family history of type 2 diabetes.
  • You're African-American, Hispanic, American Indian, Asian-American or a Pacific Islander.
  • You developed gestational diabetes when you were pregnant or gave birth to a baby who weighed more than 9 pounds (4.1 kilograms).
  • You have polycystic ovary syndrome, a common condition characterized by irregular menstrual periods, excess hair growth and obesity.
  • You have high blood pressure.
  • Your high-density lipoprotein (HDL) cholesterol (the "good" cholesterol) is below 35 milligrams per deciliter (mg/dL) — 0.9 millimoles per liter or mmol/L — or your triglyceride level is above 250 mg/dL (2.83 mmol/L).
  • You regularly sleep fewer than six hours or more than nine hours a night.
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Causes

The exact cause of prediabetes is unknown, although researchers have discovered some genes that are related to insulin resistance. Excess fat — especially abdominal fat — and inactivity also seem to be important factors in the development of prediabetes.

What is clear is that people who have prediabetes aren't quite processing sugar (glucose) properly anymore. This causes sugar to build up in the bloodstream instead of doing its normal job of fueling the cells that make up muscles and other tissues.

Most of the glucose in your body comes from the foods you eat, specifically foods that contain carbohydrates. Any food that contains carbohydrates can affect your blood sugar levels, not just sweet foods.

During digestion, sugar enters your bloodstream and with the help of insulin is then absorbed into the body's cells to give them energy.

Insulin is a hormone that comes from the pancreas, a gland located just behind the stomach. When you eat, your pancreas secretes insulin into your bloodstream. As insulin circulates, it acts like a key that unlocks microscopic doors that allow sugar to enter your cells. Insulin lowers the amount of sugar in your bloodstream. As your blood sugar level drops, so does the secretion of insulin from your pancreas.

When you have prediabetes, this process begins to work improperly. Instead of fueling your cells, sugar builds up in your bloodstream. This occurs when your pancreas doesn't make enough insulin or your cells become resistant to the action of insulin or both.

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Risk factors

The same factors that increase the risk of developing type 2 diabetes increase the risk of developing prediabetes, including:

  • Extra weight. Being overweight is a primary risk factor for prediabetes. The more fatty tissue you have — especially inside and between the muscle and skin around your abdomen — the more resistant your cells become to insulin.
  • Inactivity. The less active you are, the greater your risk of prediabetes. Physical activity helps you control your weight, uses up glucose as energy and makes your cells more sensitive to insulin.
  • Advancing age. The risk of prediabetes increases as you get older, especially after age 45. This may be because people tend to exercise less, lose muscle mass and gain weight as they age. However, older people aren't the only ones at risk of prediabetes and type 2 diabetes. The incidence of these disorders is also rising in younger age groups.
  • Family history. The risk of prediabetes increases if a parent or sibling has type 2 diabetes.
  • Race. Although it's unclear why, people of certain races — including African-Americans, Hispanics, American Indians, Asian-Americans and Pacific Islanders — are more likely to develop prediabetes.
  • Gestational diabetes. If you developed gestational diabetes when you were pregnant, your risk of later developing diabetes increases. If you gave birth to a baby who weighed more than 9 pounds (4.1 kilograms), you're also at increased risk of diabetes.
  • Polycystic ovary syndrome. For women, having polycystic ovary syndrome — a common condition characterized by irregular menstrual periods, excess hair growth and obesity — increases the risk of diabetes.
  • Sleep. Several recent studies have linked a lack of sleep or too much sleep to an increased risk of insulin resistance. Research suggests that regularly sleeping fewer than six hours or more than nine hours a night might up your risk of prediabetes or type 2 diabetes.

Other conditions associated with diabetes include:

  • High blood pressure
  • Low levels of HDL, or the "good" cholesterol
  • High levels of triglycerides — a type of fat in your blood

When these conditions — high blood pressure, high blood sugar, and abnormal blood fats and cholesterol — occur together along with obesity, they are associated with resistance to insulin. This is often referred to as metabolic syndrome.

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Complications

Progression into type 2 diabetes is the most serious consequence of untreated prediabetes.

Type 2 diabetes complications include:

  • High blood pressure
  • High cholesterol
  • Heart disease
  • Stroke
  • Kidney disease
  • Blindness
  • Amputations
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Preparing for your appointment

You're likely to start by seeing your family doctor or a general practitioner. However, you may then be referred to a doctor who specializes in diabetes treatment (endocrinologist).

Here's some information to help you get ready for your appointment and know what to expect from your doctor.

What you can do

  • Be aware of any pre-appointment restrictions. When you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet. You'll probably need to fast for eight to 10 hours before your appointment so your doctor can measure your fasting blood sugar level.
  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Make a list of all medications, vitamins or supplements you're taking.
  • Write down questions to ask your doctor.

Preparing a list of questions can help you make the most of your time with your doctor. For prediabetes, some basic questions to ask your doctor include:

  • How can I prevent prediabetes from turning into type 2 diabetes?
  • Is there a medication I can take?
  • What types of side effects can I expect from medication?
  • I have other health conditions. How can I best manage them together?
  • How much exercise do I need?
  • Are there foods I need to avoid? Can I still eat sugar?
  • Do I need to see a dietitian?
  • Are there brochures or other printed material I can take with me? What websites do you recommend?

Don't hesitate to ask any other questions that occur to you. Be sure you understand your doctor's recommendations.

What to expect from your doctor
Your doctor is likely to ask you questions, such as:

  • Has your weight changed recently?
  • Do you exercise regularly? If so, for how long and how often?
  • Do you have a family history of diabetes?
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Tests and diagnosis

Who should be tested
The American Diabetes Association recommends blood glucose screening if you have any risk factors for prediabetes. This includes if you:

  • Are overweight, with a body mass index above 25
  • Are inactive
  • Are age 45 or older
  • Have a family history of type 2 diabetes
  • Are African-American, Hispanic, American Indian, Asian-American or a Pacific Islander
  • Have a history of gestational diabetes or have given birth to a baby who weighed more than 9 pounds (4.1 kilograms)
  • Have a history of polycystic ovary syndrome
  • Have high blood pressure
  • Have abnormal cholesterol levels, including a high-density lipoprotein (HDL) cholesterol below 35 mg/dL (0.9 mmol/L) or triglyceride level above 250 mg/dL (2.83 mmol/L)

Tests used to diagnose prediabetes
In June 2009, an international committee composed of experts from the American Diabetes Association, the European Association for the Study of Diabetes and the International Diabetes Federation recommended that prediabetes testing include the:

  • Glycated hemoglobin (A1C) test. This blood test indicates your average blood sugar level for the past two to three months. It works by measuring the percentage of blood sugar attached to hemoglobin, the oxygen-carrying protein in red blood cells. The higher your blood sugar levels, the more hemoglobin you'll have with sugar attached. An A1C level between 6 and 6.5 percent is considered prediabetes. A level of 6.5 percent or higher on two separate tests indicates you have diabetes.

    Certain conditions can make the A1C test inaccurate — such as if you are pregnant or have an uncommon form of hemoglobin (known as a hemoglobin variant).

Following are other tests that your doctor may use to diagnose prediabetes:

  • Fasting blood sugar test. A blood sample will be taken after you fast for at least eight hours or overnight. With this test, a blood sugar level lower than 100 milligrams per deciliter (mg/dL) — 5.6 millimoles per liter (mmol/L) — is normal. A blood sugar level from 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is considered prediabetes. This is sometimes referred to as impaired fasting glucose (IFG). A blood sugar level of 126 mg/dL (7.0 mmol/L) or higher may indicate diabetes mellitus.
  • Oral glucose tolerance test. A blood sample will be taken after you fast for at least eight hours or overnight. Then you'll drink a sugary solution, and your blood sugar level will be measured again after two hours. A blood sugar level less than 140 mg/dL (7.8 mmol/L) is normal. A blood sugar level from 140 to 199 mg/dL (7.8 to 11.0 mmol/L) is considered prediabetes. This is sometimes referred to as impaired glucose tolerance (IGT). A blood sugar level of 200 mg/dL (11.1 mmol/L) or higher may indicate diabetes mellitus.

If your blood sugar level is normal, your doctor may recommend a screening test every three years. If you have prediabetes, further testing may be needed. For example, your doctor should check your fasting blood sugar, A1C, total cholesterol, HDL cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides at least once a year, possibly more frequently if you have additional risk factors for diabetes. Your doctor may also recommend an annual microalbuminuria test, which checks for protein in your urine — an early sign of damage to the kidneys.

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Treatments and drugs

If you have prediabetes, healthy lifestyle choices can help you bring your blood sugar level back to normal or at least keep it from rising toward the levels seen in type 2 diabetes. Guidelines from the American College of Endocrinology suggest the following to treat prediabetes:

  • Eat healthy foods. Choose foods low in fat and calories and high in fiber. Focus on fruits, vegetables and whole grains. Strive for variety to help you achieve your goals without compromising taste or nutrition.
  • Get more physical activity. Aim for 30 to 60 minutes of moderate physical activity at least five days a week. Take a brisk daily walk. Ride your bike. Swim laps. If you can't fit in a long workout, break it up into smaller sessions spread throughout the day.
  • Lose excess pounds. If you're overweight, losing just 5 to 10 percent of your body weight — only 10 to 20 pounds (4.5 to 9 kilograms) if you weigh 200 pounds (91 kilograms) — can reduce the risk of developing type 2 diabetes. To keep your weight in a healthy range, focus on permanent changes to your eating and exercise habits. Motivate yourself by remembering the benefits of losing weight, such as a healthier heart, more energy and improved self-esteem.
  • Take medications as needed. Sometimes medications — such as the oral diabetes drugs metformin (Glucophage) and acarbose (Precose) — also are an option if you're at high risk of diabetes. This includes if your prediabetes is worsening or you have cardiovascular disease, fatty liver disease or polycystic ovary syndrome. Some studies have indicated that pioglitazone (Actos) and similar drugs, which improve insulin sensitivity, might help reduce the risk of converting from prediabetes to diabetes, but were associated with weight gain and water retention (edema).

In other cases, medications to control cholesterol — statins, in particular — and medications to control high blood pressure are needed. Healthy lifestyle choices remain essential, however.

Because the findings from several recent studies suggest that regularly getting a good night of sleep may reduce insulin resistance, try to get at least six hours or more of sleep each night.

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Alternative medicine

Many alternative therapies — including cassia cinnamon, chromium, ginseng, glucomannan, guar gum, gymnema, magnesium, milk thistle, prickly pear cactus, soy and stevia — have been touted as possible ways to treat or prevent type 2 diabetes. Although some of these substances have shown promise in early trials, there's no definitive evidence that any of these alternative therapies are effective.

If you're considering dietary supplements or other alternative therapies to treat or prevent prediabetes, consult your doctor. He or she can help you weigh the pros and cons of specific alternative therapies.

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Prevention

Healthy lifestyle choices can help you prevent prediabetes and its progression to type 2 diabetes — even if diabetes runs in your family.

  • Eat healthy foods.
  • Get more physical activity.
  • Lose excess pounds.

The same lifestyle changes that can treat or even reverse prediabetes help prevent the condition, too.

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